Note 4 - Loans and Allowance for Credit Losses (Detail) - Allowance For Credit Losses By Portfolio Segment (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Allowance for credit losses:
Balance at beginning of period	$ 37,492	$ 29,653
Loans charged-off	(2,083)	(1,853)
Recoveries of loans previously charged-off	37	105
Net loan charged-off	(2,046)	(1,748)
Provision for credit losses	3,365	3,970
Ending balance	38,811	31,875
Allowance for credit losses:
Individually evaluated for impairment	7,458	5,945
Collectively evaluated for impairment	31,353	25,930
March 31, 2012
Ending balance	38,811	31,875	37,492
Commercial Loan [Member]
Allowance for credit losses:
Balance at beginning of period	9,412	9,609
Loans charged-off	(1,184)	(773)
Recoveries of loans previously charged-off	26	7
Net loan charged-off	(1,158)	(766)
Provision for credit losses	2,821	(306)
Ending balance	11,075
Allowance for credit losses:
Individually evaluated for impairment	2,360	1,874
Collectively evaluated for impairment	8,715	6,663
March 31, 2012
Ending balance		8,537
Commercial Real Estate Investment [Member]
Allowance for credit losses:
Balance at beginning of period	9,148	7,304
Loans charged-off	(109)	(291)
Recoveries of loans previously charged-off		2
Net loan charged-off	(109)	(289)
Provision for credit losses	(32)	1,130
Ending balance	9,007
Allowance for credit losses:
Individually evaluated for impairment	818	829
Collectively evaluated for impairment	8,189	7,316
March 31, 2012
Ending balance		8,145
Commercial Real Estate Owner Occupied [Member]
Allowance for credit losses:
Balance at beginning of period	2,781	1,898
Provision for credit losses	23	248
Ending balance	2,804
Allowance for credit losses:
Individually evaluated for impairment	704	201
Collectively evaluated for impairment	2,100	1,945
March 31, 2012
Ending balance		2,146
Residential Mortgage [Member]
Allowance for credit losses:
Balance at beginning of period	659	399
Loans charged-off		(300)
Net loan charged-off		(300)
Provision for credit losses	218	(99)
Ending balance	877
Allowance for credit losses:
Collectively evaluated for impairment	877
Home Equity Line of Credit [Member]
Allowance for credit losses:
Balance at beginning of period	1,730	1,528
Loans charged-off	(29)	(244)
Recoveries of loans previously charged-off		1
Net loan charged-off	(29)	(243)
Provision for credit losses	51	44
Ending balance	1,752
Allowance for credit losses:
Individually evaluated for impairment	218	138
Collectively evaluated for impairment	1,534	1,191
March 31, 2012
Ending balance		1,329
Consumer, Other [Member]
Allowance for credit losses:
Balance at beginning of period	371	369
Loans charged-off	(42)	(5)
Recoveries of loans previously charged-off	5	1
Net loan charged-off	(37)	(4)
Provision for credit losses	17	(307)
Ending balance	351
Allowance for credit losses:
Individually evaluated for impairment		4
Collectively evaluated for impairment	351	54
March 31, 2012
Ending balance		58
Construction Loans [Member]
Allowance for credit losses:
Balance at beginning of period	13,391	8,546
Loans charged-off	(719)	(240)
Recoveries of loans previously charged-off	6	94
Net loan charged-off	(713)	(146)
Provision for credit losses	267	3,260
Ending balance	12,945
Allowance for credit losses:
Individually evaluated for impairment	3,358	2,899
Collectively evaluated for impairment	9,587	8,761
March 31, 2012
Ending balance		$ 11,660